Alpha-linolenic acid (ALA; n-3 18:3), a one of omega-3 fatty acid, is mainly contained in chloroplast of plant and ALA is an essential fatty acid, not synthesized in mammalian body, it must be supplied from foods. Polyspermy is especially high on in vitro fertilization (IVF) in pigs, which is a major obstacle to in vitro embryo production systems. In our previous study, when ALA was supplemented during in vitro maturation (IVM), the methaphase-II rate and gluthathione level was increased. The objective of this study was to evaluate the effects of alpha-linolenic acid (ALA) supplementation during IVM and subsequent of IVF in pigs. The cumulus-oocyte complexes (COCs) were submitted to IVM medium containing 0, 25, 50, and 100 μM ALA for 44 h. After 44 h of IVM, denuded oocytes were co-cultured with spermatozoa during 18 h. After 18 h of in vitro fertilization, oocyte were using aceto-orcein method, to evaluated penetration rate, monospermy (number of monospermy oocytes/total oocytes), and the IVF efficiency (number of monospermy/total penetrated oocytes). In results, 25 and 50 μM ALA groups were significantly increased on penetration rate compared with 100 μM ALA group (p<0.05). Similarly, monospermy rate were significantly increased 25 and 50 μM ALA groups than control group (p<0.05). IVF efficiency was no significant difference between control and ALA treatment groups. Our findings suggested that treatment of ALA supplementation during in vitro maturation (IVM) and subsequent of in vitro fertilization in pigs, ALA can increase IVF efficiency by effectively blocking polyspermy and increasing monospermy some mechanism in porcine oocytes. However, the study of mechanism by which ALA blocks polyspermy are needed, and this study suggests that ALA has a positive effect on in vitro production of porcine oocytes by decreasing polyspermy. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (Ministry of Education) (2016R1D1A1B03931746).